The invention relates to a rear projection screen comprising a first plate, a first side of which has a lenticular structure, and a second plate, a first side of which has a Fresnel structure with a plurality of Fresnel facets enclosing an angle .psi. with the plane of the screen, a second side of the first plate and the first side of the second plate facing each other.
The invention also relates to a rear projection system comprising projection modules which can be stacked and are provided with such a rear projection screen.
A projection screen of the type described in the opening paragraph is known from, for example U.S. Pat. No. 4,919,518. This patent describes a projection screen with a Fresnel lens, a prism structure and a lenticular structure. The light to be projected is incident on the Fresnel structure and leaves the screen via the lenticular structure. An important requirement for such a projection screen is that it has a sufficient stability.
A sufficient stability can be realized in different manners. A first possibility is to render the lens structures, in other words, the Fresnel structure and the lenticular structure, sufficiently rigid by themselves by choosing the lens plates to be thick enough. However, this has the drawback that reflections in a relatively thick plate give rise to ghost images.
Another possibility is to provide a relatively thin lens plate, such as, for example a lens foil, on a separate substrate. This has the drawback that extra surfaces are created in this way, on which unwanted reflections will occur. Moreover, there will be loss of light due to light absorption in the substrate. Furthermore, the risk of accumulation of moisture between the surface of the unstable lens structure and the surface of the substrate will be considerably large as a result of the air humidity.
A further drawback of the known projection screens, notably in the case of a projection screen comprising stacked modules, is that the lens structures are exactly equally large and that it is impossible to fix them to each other without disturbing the image at the edges of a module.